If the sintering temperature is too high, the growth ra […]
If the sintering temperature is too high, the growth rate of titanium carbide grains will increase. The final sintering temperature of titanium carbide and high manganese steel-bonded cemented carbide is generally 1420℃. Titanium plate manufacturers believe that the sintering temperature should not be too high. Even the bonding phase becomes the liquid phase and the metal is lost, so that the hard phase abuts, aggregates and grows up, forming a source of fragmentation. This is the reason why the bonding phase between the hard phase crystal grains analyzed earlier has become less.
Of course, the sintering temperature should not be too low, otherwise the alloy will be under-burned. In addition to the aforementioned need to control the sintering temperature and speed, the vacuum in the furnace enters the liquid phase sintering stage. It is also necessary to control the vacuum degree in the furnace during sintering, because too high a vacuum degree will volatilize a large amount of liquid metal and cause component segregation. Especially in the three stages of degumming, reduction and liquid phase sintering, the heating rate during sintering is not suitable for such alloys.
Strictly control the heating rate and holding time. Because in the low-temperature degumming stage, the compaction releases the compression stress and the forming agent volatilizes. If the heating speed is fast, the forming agent is too late to volatilize and becomes steam after liquefaction, causing the compaction to burst or microcrack; above 900℃ In the reduction stage, the green compact should have enough time to remove the volatiles and oxygen in the raw material powder (such as Mn2Fe master alloy); when entering the liquid phase sintering stage, the heating rate should also be slowed down to fully alloy the green compact.
In the same conditions, industrial titanium plates with different compositions will show different decarburization behaviors. For example, Si can improve the elastic limit, strength, tempering stability, and elastic decline resistance, because different alloying elements have different effects on the activity and diffusion of carbon. However, attention must also be paid to the serious decarburization of the surface caused by the increase in the activity of carbon in austenite and the chemical potential gradient caused by Si.
Titanium plate manufacturers believe that the surface strength of parts is an important factor affecting fatigue strength. Surface heat treatment and surface cold plastic deformation processing are very effective in improving fatigue strength. Reduce fatigue crack formation. Grinding off the surface decarburized layer produced by heat treatment can significantly increase the fatigue limit; direct shot peening without removing the surface decarburized layer produced after heat treatment can increase the fatigue limit more than after removing decarburization, such as surface quenching and carburizing , Carbonitriding, nitriding, shot peening and rolling.